Please add param.h before the occurrences of sysctl.h in configure.in:278 as well (https://support.zabbix.com/browse/ZBX-224 - however: forget my attached code, its bollocks).

Also, swap.h (configure.in:302) requires the inclusion of param.h (http://www.openbsd.org/cgi-bin/man.cgi?query=swapctl&apropos=0&sektion=2&manpath=OpenBSD+Current&arch=i386&format=html), please add that as well:
---------8<---------
diff -Nur trunk/configure.in.orig trunk/configure.in
— trunk/configure.in.orig 2008-01-15 12:20:24.000000000 +0100
+++ trunk/configure.in 2008-01-15 12:49:45.000000000 +0100
@@ -298,6 +299,7 @@
[
#include <stdlib.h>
#include <sys/types.h>
+#include <sys/param.h>
#include <sys/syscall.h>
#include <sys/swap.h>
],
---------8<---------

And please close https://support.zabbix.com/browse/ZBX-249 since it seems to have been fixed in this revision as well.

Keep up the good work
Sebastian